GenericGFPoly::isZero() - Code Metrics - Inspection of ":octocat: moved readme images" - chillerlan/php-qrcode - Measure and Improve Code Quality continuously with Scrutinizer

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by smiley

created 2021-11-18 11:49 UTC

GenericGFPoly::isZero() A

↳ Parent: GenericGFPoly

Complexity

Conditions	1
Paths	1

Size

Total Lines	2
Code Lines	1

Duplication

Lines	0
Ratio	0 %

Importance

Changes	1
Bugs	0	Features	0

Metric	Value
cc	1
eloc	1
nc	1
nop	0
dl	0
loc	2
rs	10
c	1
b	0
f	0

<?php
/**
 * Class GenericGFPoly
 *
 * @created      16.01.2021
 * @author       ZXing Authors
 * @author       Smiley <[email protected]>
 * @copyright    2021 Smiley
 * @license      Apache-2.0
 */

namespace chillerlan\QRCode\Common;

use InvalidArgumentException;

use function array_fill, array_slice, array_splice, count;

/**
 * <p>Represents a polynomial whose coefficients are elements of a GF.
 * Instances of this class are immutable.</p>
 *
 * <p>Much credit is due to William Rucklidge since portions of this code are an indirect
 * port of his C++ Reed-Solomon implementation.</p>
 *
 * @author Sean Owen
 */
final class GenericGFPoly{

	private array $coefficients;

	/**
	 * @param array      $coefficients array coefficients as ints representing elements of GF(size), arranged
	 *                                 from most significant (highest-power term) coefficient to least significant
	 * @param int|null   $degree
	 *
	 * @throws \InvalidArgumentException if argument is null or empty, or if leading coefficient is 0 and this is not a
	 *                                  constant polynomial (that is, it is not the monomial "0")
	 */
	public function __construct(array $coefficients, int $degree = null){
		$degree ??= 0;

		if(empty($coefficients)){
			throw new InvalidArgumentException('arg $coefficients is empty');
		}

		if($degree < 0){
			throw new InvalidArgumentException('negative degree');
		}

		$coefficientsLength = count($coefficients);

		// Leading term must be non-zero for anything except the constant polynomial "0"
		$firstNonZero = 0;

		while($firstNonZero < $coefficientsLength && $coefficients[$firstNonZero] === 0){
			$firstNonZero++;
		}

		if($firstNonZero === $coefficientsLength){
			$this->coefficients = [0];
		}
		else{
			$this->coefficients = array_fill(0, $coefficientsLength - $firstNonZero + $degree, 0);

			for($i = 0; $i < $coefficientsLength - $firstNonZero; $i++){
				$this->coefficients[$i] = $coefficients[$i + $firstNonZero];
			}
		}
	}

	/**
	 * @return int $coefficient of x^degree term in this polynomial
	 */
	public function getCoefficient(int $degree):int{
		return $this->coefficients[count($this->coefficients) - 1 - $degree];
	}

	/**
	 * @return int[]
	 */
	public function getCoefficients():array{
		return $this->coefficients;
	}

	/**
	 * @return int $degree of this polynomial
	 */
	public function getDegree():int{
		return count($this->coefficients) - 1;
	}

	/**
	 * @return bool true if this polynomial is the monomial "0"
	 */
	public function isZero():bool{
		return $this->coefficients[0] === 0;
	}

	/**
	 * @return int evaluation of this polynomial at a given point
	 */
	public function evaluateAt(int $a):int{

		if($a === 0){
			// Just return the x^0 coefficient
			return $this->getCoefficient(0);
		}

		$result = 0;

		foreach($this->coefficients as $c){
			// if $a === 1 just the sum of the coefficients
			$result = GF256::addOrSubtract(($a === 1 ? $result : GF256::multiply($a, $result)), $c);
		}

		return $result;
	}

	/**
	 * @param \chillerlan\QRCode\Common\GenericGFPoly $other
	 *
	 * @return \chillerlan\QRCode\Common\GenericGFPoly
	 */
	public function multiply(GenericGFPoly $other):GenericGFPoly{

		if($this->isZero() || $other->isZero()){
			return new self([0]);
		}

		$product = array_fill(0, count($this->coefficients) + count($other->coefficients) - 1, 0);

		foreach($this->coefficients as $i => $aCoeff){
			foreach($other->coefficients as $j => $bCoeff){
				$product[$i + $j] ^= GF256::multiply($aCoeff, $bCoeff);
			}
		}

		return new self($product);
	}

	/**
	 * @param \chillerlan\QRCode\Common\GenericGFPoly $other
	 *
	 * @return \chillerlan\QRCode\Common\GenericGFPoly[] [quotient, remainder]
	 */
	public function divide(GenericGFPoly $other):array{

		if($other->isZero()){
			throw new InvalidArgumentException('Division by 0');
		}

		$quotient  = new self([0]);
		$remainder = clone $this;

		$denominatorLeadingTerm        = $other->getCoefficient($other->getDegree());
		$inverseDenominatorLeadingTerm = GF256::inverse($denominatorLeadingTerm);

		while($remainder->getDegree() >= $other->getDegree() && !$remainder->isZero()){
			$scale     = GF256::multiply($remainder->getCoefficient($remainder->getDegree()), $inverseDenominatorLeadingTerm);
			$diff      = $remainder->getDegree() - $other->getDegree();
			$quotient  = $quotient->addOrSubtract(GF256::buildMonomial($diff, $scale));
			$remainder = $remainder->addOrSubtract($other->multiplyByMonomial($diff, $scale));
		}

		return [$quotient, $remainder];

	}

	/**
	 * @param int $scalar
	 *
	 * @return \chillerlan\QRCode\Common\GenericGFPoly
	 */
	public function multiplyInt(int $scalar):GenericGFPoly{

		if($scalar === 0){
			return new self([0]);
		}

		if($scalar === 1){
			return $this;
		}

		$product = array_fill(0, count($this->coefficients), 0);

		foreach($this->coefficients as $i => $c){
			$product[$i] = GF256::multiply($c, $scalar);
		}

		return new self($product);
	}

	/**
	 * @param int $degree
	 * @param int $coefficient
	 *
	 * @return \chillerlan\QRCode\Common\GenericGFPoly
	 */
	public function multiplyByMonomial(int $degree, int $coefficient):GenericGFPoly{

		if($degree < 0){
			throw new InvalidArgumentException();
		}

		if($coefficient === 0){
			return new self([0]);
		}

		$product = array_fill(0, count($this->coefficients) + $degree, 0);

		foreach($this->coefficients as $i => $c){
			$product[$i] = GF256::multiply($c, $coefficient);
		}

		return new self($product);
	}

	/**
	 * @param \chillerlan\QRCode\Common\GenericGFPoly $other
	 *
	 * @return \chillerlan\QRCode\Common\GenericGFPoly
	 */
	public function mod(GenericGFPoly $other):GenericGFPoly{

		if(count($this->coefficients) - count($other->coefficients) < 0){
			return $this;
		}

		$ratio = GF256::log($this->coefficients[0]) - GF256::log($other->coefficients[0]);

		foreach($other->coefficients as $i => $c){
			$this->coefficients[$i] ^= GF256::exp(GF256::log($c) + $ratio);
		}

		return (new self($this->coefficients))->mod($other);
	}

	/**
	 * @param \chillerlan\QRCode\Common\GenericGFPoly $other
	 *
	 * @return \chillerlan\QRCode\Common\GenericGFPoly
	 */
	public function addOrSubtract(GenericGFPoly $other):GenericGFPoly{

		if($this->isZero()){
			return $other;
		}

		if($other->isZero()){
			return $this;
		}

		$smallerCoefficients = $this->coefficients;
		$largerCoefficients  = $other->coefficients;

		if(count($smallerCoefficients) > count($largerCoefficients)){
			$temp                = $smallerCoefficients;
			$smallerCoefficients = $largerCoefficients;
			$largerCoefficients  = $temp;
		}

		$sumDiff    = array_fill(0, count($largerCoefficients), 0);
		$lengthDiff = count($largerCoefficients) - count($smallerCoefficients);
		// Copy high-order terms only found in higher-degree polynomial's coefficients
		array_splice($sumDiff, 0, $lengthDiff, array_slice($largerCoefficients, 0, $lengthDiff));

		$countLargerCoefficients = count($largerCoefficients);

		for($i = $lengthDiff; $i < $countLargerCoefficients; $i++){
			$sumDiff[$i] = GF256::addOrSubtract($smallerCoefficients[$i - $lengthDiff], $largerCoefficients[$i]);
		}

		return new self($sumDiff);
	}

}


1			<?php
2			/**
3			* Class GenericGFPoly
4			*
5			* @created 16.01.2021
6			* @author ZXing Authors
7			* @author Smiley <[email protected]>
8			* @copyright 2021 Smiley
9			* @license Apache-2.0
10			*/
11
12			namespace chillerlan\QRCode\Common;
13
14			use InvalidArgumentException;
15
16			use function array_fill, array_slice, array_splice, count;
17
18			/**
19			* <p>Represents a polynomial whose coefficients are elements of a GF.
20			* Instances of this class are immutable.</p>
21			*
22			* <p>Much credit is due to William Rucklidge since portions of this code are an indirect
23			* port of his C++ Reed-Solomon implementation.</p>
24			*
25			* @author Sean Owen
26			*/
27			final class GenericGFPoly{
28
29			private array $coefficients;
30
31			/**
32			* @param array $coefficients array coefficients as ints representing elements of GF(size), arranged
33			* from most significant (highest-power term) coefficient to least significant
34			* @param int\|null $degree
35			*
36			* @throws \InvalidArgumentException if argument is null or empty, or if leading coefficient is 0 and this is not a
37			* constant polynomial (that is, it is not the monomial "0")
38			*/
39			public function __construct(array $coefficients, int $degree = null){
40			$degree ??= 0;
41
42			if(empty($coefficients)){
43			throw new InvalidArgumentException('arg $coefficients is empty');
44			}
45
46			if($degree < 0){
47			throw new InvalidArgumentException('negative degree');
48			}
49
50			$coefficientsLength = count($coefficients);
51
52			// Leading term must be non-zero for anything except the constant polynomial "0"
53			$firstNonZero = 0;
54
55			while($firstNonZero < $coefficientsLength && $coefficients[$firstNonZero] === 0){
56			$firstNonZero++;
57			}
58
59			if($firstNonZero === $coefficientsLength){
60			$this->coefficients = [0];
61			}
62			else{
63			$this->coefficients = array_fill(0, $coefficientsLength - $firstNonZero + $degree, 0);
64
65			for($i = 0; $i < $coefficientsLength - $firstNonZero; $i++){
66			$this->coefficients[$i] = $coefficients[$i + $firstNonZero];
67			}
68			}
69			}
70
71			/**
72			* @return int $coefficient of x^degree term in this polynomial
73			*/
74			public function getCoefficient(int $degree):int{
75			return $this->coefficients[count($this->coefficients) - 1 - $degree];
76			}
77
78			/**
79			* @return int[]
80			*/
81			public function getCoefficients():array{
82			return $this->coefficients;
83			}
84
85			/**
86			* @return int $degree of this polynomial
87			*/
88			public function getDegree():int{
89			return count($this->coefficients) - 1;
90			}
91
92			/**
93			* @return bool true if this polynomial is the monomial "0"
94			*/
95			public function isZero():bool{
96			return $this->coefficients[0] === 0;
97			}
98
99			/**
100			* @return int evaluation of this polynomial at a given point
101			*/
102			public function evaluateAt(int $a):int{
103
104			if($a === 0){
105			// Just return the x^0 coefficient
106			return $this->getCoefficient(0);
107			}
108
109			$result = 0;
110
111			foreach($this->coefficients as $c){
112			// if $a === 1 just the sum of the coefficients
113			$result = GF256::addOrSubtract(($a === 1 ? $result : GF256::multiply($a, $result)), $c);
114			}
115
116			return $result;
117			}
118
119			/**
120			* @param \chillerlan\QRCode\Common\GenericGFPoly $other
121			*
122			* @return \chillerlan\QRCode\Common\GenericGFPoly
123			*/
124			public function multiply(GenericGFPoly $other):GenericGFPoly{
125
126			if($this->isZero() \|\| $other->isZero()){
127			return new self([0]);
128			}
129
130			$product = array_fill(0, count($this->coefficients) + count($other->coefficients) - 1, 0);
131
132			foreach($this->coefficients as $i => $aCoeff){
133			foreach($other->coefficients as $j => $bCoeff){
134			$product[$i + $j] ^= GF256::multiply($aCoeff, $bCoeff);
135			}
136			}
137
138			return new self($product);
139			}
140
141			/**
142			* @param \chillerlan\QRCode\Common\GenericGFPoly $other
143			*
144			* @return \chillerlan\QRCode\Common\GenericGFPoly[] [quotient, remainder]
145			*/
146			public function divide(GenericGFPoly $other):array{
147
148			if($other->isZero()){
149			throw new InvalidArgumentException('Division by 0');
150			}
151
152			$quotient = new self([0]);
153			$remainder = clone $this;
154
155			$denominatorLeadingTerm = $other->getCoefficient($other->getDegree());
156			$inverseDenominatorLeadingTerm = GF256::inverse($denominatorLeadingTerm);
157
158			while($remainder->getDegree() >= $other->getDegree() && !$remainder->isZero()){
159			$scale = GF256::multiply($remainder->getCoefficient($remainder->getDegree()), $inverseDenominatorLeadingTerm);
160			$diff = $remainder->getDegree() - $other->getDegree();
161			$quotient = $quotient->addOrSubtract(GF256::buildMonomial($diff, $scale));
162			$remainder = $remainder->addOrSubtract($other->multiplyByMonomial($diff, $scale));
163			}
164
165			return [$quotient, $remainder];
166
167			}
168
169			/**
170			* @param int $scalar
171			*
172			* @return \chillerlan\QRCode\Common\GenericGFPoly
173			*/
174			public function multiplyInt(int $scalar):GenericGFPoly{
175
176			if($scalar === 0){
177			return new self([0]);
178			}
179
180			if($scalar === 1){
181			return $this;
182			}
183
184			$product = array_fill(0, count($this->coefficients), 0);
185
186			foreach($this->coefficients as $i => $c){
187			$product[$i] = GF256::multiply($c, $scalar);
188			}
189
190			return new self($product);
191			}
192
193			/**
194			* @param int $degree
195			* @param int $coefficient
196			*
197			* @return \chillerlan\QRCode\Common\GenericGFPoly
198			*/
199			public function multiplyByMonomial(int $degree, int $coefficient):GenericGFPoly{
200
201			if($degree < 0){
202			throw new InvalidArgumentException();
203			}
204
205			if($coefficient === 0){
206			return new self([0]);
207			}
208
209			$product = array_fill(0, count($this->coefficients) + $degree, 0);
210
211			foreach($this->coefficients as $i => $c){
212			$product[$i] = GF256::multiply($c, $coefficient);
213			}
214
215			return new self($product);
216			}
217
218			/**
219			* @param \chillerlan\QRCode\Common\GenericGFPoly $other
220			*
221			* @return \chillerlan\QRCode\Common\GenericGFPoly
222			*/
223			public function mod(GenericGFPoly $other):GenericGFPoly{
224
225			if(count($this->coefficients) - count($other->coefficients) < 0){
226			return $this;
227			}
228
229			$ratio = GF256::log($this->coefficients[0]) - GF256::log($other->coefficients[0]);
230
231			foreach($other->coefficients as $i => $c){
232			$this->coefficients[$i] ^= GF256::exp(GF256::log($c) + $ratio);
233			}
234
235			return (new self($this->coefficients))->mod($other);
236			}
237
238			/**
239			* @param \chillerlan\QRCode\Common\GenericGFPoly $other
240			*
241			* @return \chillerlan\QRCode\Common\GenericGFPoly
242			*/
243			public function addOrSubtract(GenericGFPoly $other):GenericGFPoly{
244
245			if($this->isZero()){
246			return $other;
247			}
248
249			if($other->isZero()){
250			return $this;
251			}
252
253			$smallerCoefficients = $this->coefficients;
254			$largerCoefficients = $other->coefficients;
255
256			if(count($smallerCoefficients) > count($largerCoefficients)){
257			$temp = $smallerCoefficients;
258			$smallerCoefficients = $largerCoefficients;
259			$largerCoefficients = $temp;
260			}
261
262			$sumDiff = array_fill(0, count($largerCoefficients), 0);
263			$lengthDiff = count($largerCoefficients) - count($smallerCoefficients);
264			// Copy high-order terms only found in higher-degree polynomial's coefficients
265			array_splice($sumDiff, 0, $lengthDiff, array_slice($largerCoefficients, 0, $lengthDiff));
266
267			$countLargerCoefficients = count($largerCoefficients);
268
269			for($i = $lengthDiff; $i < $countLargerCoefficients; $i++){
270			$sumDiff[$i] = GF256::addOrSubtract($smallerCoefficients[$i - $lengthDiff], $largerCoefficients[$i]);
271			}
272
273			return new self($sumDiff);
274			}
275
276			}
277

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GenericGFPoly::isZero() A

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